High-speed textile yarn winders normally employ a synchronous motor to rotate a surface drive roller which in turn rotates a package core and applies incoming yarn thereabout. Such yarn is distributed axially along the rotating package core by a reciprocating traverse device, which is driven by a separate motor. One such winder is disclosed, for example, in Schippers et al U.S. Pat. No. 3,861,607,.sup.(+) which is, to the extent deemed necessary for full understanding of the present invention, hereby incorporated herein by reference. FNT .sup.(+) or Peckingpaugh U.S. Pat. No. 3,799,463
Each motor type normally receives alternating current from a separate frequency converter, consisting of an AC to DC converter and a DC to AC inverter. Completely separate frequency converters have been considered necessary because the surface drive roller requires constant speed, while the reciprocation rate of the traverse device is recurrently varied by, for example, up to five percent of average speed in order to avoid undesirable patterns in the yarn package as deposited on the core. Thus, one converter supplies a preset constant frequency, while the other supplies frequency which recurrently varies responsive to a control signal delivered to the converter. The traverse motor responds to this varying frequency by recurrently accelerating and decelerating between upper and lower speed limits. Further, the required average traverse motor speed and voltage/frequency ratio is often substantially different from that required by the package drive roll motor, although at times such values may be nearly the same.
During recurrent deceleration, the traverse device motors generate a back EMF. Heretofore, it has been the practice to disconnect the motor terminals from the converter during each deceleration interval and connect them to a power resistor, which dissipates the generated power as heat, and serves to dynamically brake the motor. Often, it has also been necessary to supply cooling in order to maintain the power resistor at a non-destructive temperature. Thus, this recurrently generated power is substantially wasted. Further, the converter supplying the traverse motors is made more complex and expensive by inclusion therein of the power resistor, the cooling device, and the switching network required to recurrently disconnect and reconnect the motor terminals.